How can nations engage with failed states where governmental functions have become paralysed and countries that have fallen into civil war, and prevent them from becoming hotbeds of terrorism?

Based on the lessons learnt from the 20-year “war on terror” and changes in the global situation, Japan, the United States and Europe must strengthen their unity and champion an international order based on freedom and democracy.

Twenty years have passed since the September 11, 2001, terrorist attacks on the United States, in which the international terrorist organisation al-Qaeda hijacked aircraft and struck New York and the suburbs of Washington.

The United States immediately retaliated and swept out al-Qaeda strongholds in Afghanistan. Also in that nation, the US brought down the regime of the Taleban, an Islamist group that had been harbouring al-Qaeda, with the aim of building a democratic nation.

However, with the complete withdrawal of US forces from Afghanistan in August, the Taleban have returned to power. Many people must feel helpless in this situation, in which it seems like the clock has turned back.

The war in Afghanistan was the longest war in US history. At one point, 100,000 US troops were deployed, but they were unable to destroy the Taleban, struggling to deal with terrorist attacks by the group. A total of 2,461 US soldiers were killed, and the cost of the war is said to have topped $2.31 trillion.

Al-Qaeda has been weakened, and large-scale attacks against the US and Europe by terrorists based in Afghanistan have been deterred for the past 20 years. So why does it feel like the war yielded few results?

One reason is that extremist groups and terrorist organisations have been expanding, especially in the Middle East and Africa, and have carried out terrorist acts in many places around the globe, making it difficult to feel that the world has become safer.

That the United States has declared the end of the Afghan war with the withdrawal of its troops does not mean extremism will disappear from the world. Citizens of advanced countries such as Japan, the United States and the nations of Europe can be the targets of terrorism and kidnapping anywhere in the world.

The governments of these countries should respond to the threat through the close exchange of information.

What has been the problem with the United States' antiterrorism strategy over the past 20 years? It must be rationally examined and used as a lesson for greater stability in the future.

After the war in Afghanistan, the administration of US president George W. Bush launched a war against the dictatorship in Iraq, adding democratisation to the goals of the war on terrorism, based on the idea that the US has a responsibility to spread freedom and democracy throughout the world.

While women's human rights improved in the post-Taleban Afghan regime, ethnic, religious and regional divisions among the people were never overcome. The corrupt system in which foreign aid was appropriated by senior government and military leaders remained unchanged.

Having lost the backing of the US military, Afghan government forces abandoned the fight against the Taleban. This probably illustrates that no matter how many troops and funds are introduced from outside, stability cannot be built unless a self-reliant government and armed forces are nurtured.

The international situation has changed drastically compared with 20 years ago, when the United States was the sole superpower. China is rapidly catching up with the United States in the military, economic and technological fields.

US president Joe Biden intends to focus the Americans' limited resources on competing with the big powers of China and Russia, saying that terrorism can be prevented without locally stationing US troops.

An “inward-looking mindset” persists in US public opinion. Biden has also said, “American troops cannot and should not be fighting in a war … that Afghan forces are not willing to fight for themselves”. A warning should be sounded that China and Russia will see the situation as demonstrating the United States’ weakness and step up their efforts to buffet the United States.

Of course, Afghanistan has a different importance for the United States than allies such as Japan and Europe do, as well as a different security situation. The alliance with Japan and European nations is an asset for the United States.

However, the allies should take the opportunity to deepen their recognition that their own defence efforts will strengthen the alliance with the United States and stabilise the international order. This will also serve as a check on China and Russia.

It is hard to shake the concern that terrorists and extremists will gather in Afghanistan, encouraged by the “victory” touted by the Taleban.

In the Middle East, Syria and Yemen have become virtually failed states owing to protracted civil wars. There are fears that extremist groups such as the Islamic State will once again create havens in these countries and increase their terrorist attacks on advanced nations.

In a society where the people cannot have a sense of affluence and fairness, it is difficult to eradicate the roots of terrorism. Extremism must not be allowed to spread around the world through social media.

Deterring terrorism is a challenge for the entire international community. Japan, the United States and Europe must approach China and Russia for co-operation, and strengthen steady civilian support, such as vocational training for citizens. It is also important to build a monitoring system centred around the United Nations to ensure that such efforts are steadily implemented on the front line.